Thermal Analysis in Ecotect

New York CitY College of teChNologYthe CitY UNiversitY of New York

Thermal analysis in ecoTecT

archiTecTural Technology deparTmenTwritten by nicole seekely

revised april 20, 2010 3:54 pm

notes: material thickness should not be modeled. Zones can be depicted with planar surface. Be sure you have floors, windows, voids, and partitions assigned properly.

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For proper thermal analysis, it is recommended that you model your geometry in ecotect. importing a model will result in too much unnecessary geometry that will incorrectly inform the analysis.

all zones in your model need to be compleTely enclosed, independently of other zones around them. in the example here, the roof of the green zone, overlaps the floor of the blue zone - this is oKay.

notes:

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make sure all your surface normals are pointing to the outside. To check this, go to display - surface normals. if the arrows are pointing inwards, select the element and use ctrl+r to reverse the direction of the normal.

To get rid of the normals display, go to display - model.

also, make sure all external shading devices are on a non thermal layer such as the outside zone.

notes: you can view the data for the material by double-clicking the material. click on the properties tab to see u-Value, description, and other data. click on the layers tab to view a section of the material and a break-down of the layers.

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materials:For each surface, you should set a primary and alternative material. The primary material is when the surface is in contact with the outside. The alTernaTiVe material is when the surface is in contact with another surface (ie interior wall).

With the object(s) selected, go to the material assignments tab. select both options when necessary.

notes: clicking the arrow to the right of each box will give you recommended values.

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Zone settings:you need to tell ecotect what each zone or space is used for. To do this, go to model - Zone management.

in the Zone management window, select a zone on the left to view it’s default settings. in the general settings tab you can adjust the clothing factor, lighting level, number of people, activity level, etc.

notes:

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Zone settings:click on the Thermal properties tab to further adjust settings. select your hVac system, thermostat range, and hours of operation.

notes:

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Before looking at the Thermal analysis, you’ll need to calculate your inter-zonal adjacencies. This will tell you if ecotect understands your model and will inform you of any errors. go to calculate - inter-zonal adjacencies.

all the default settings should be okay to use.

more than likely, you’ll have an error that two objects sharing a face do not have the same alternate material. Be sure to go back and fix this.

notes:

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lastly, go to the project tab on the left side. check your data and be sure your north offset is set correctly. This is an easy way to change the orientation of your building if it’s not oriented exactly to the north.

notes:

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go to the analysis tab on the left side.

here you can change several different options to do comparison analysis and gather thermal data for your building.

The following slides will take you through a few of the possible analysis you could do. most of this can be done using the options at the bottom of the screen.

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search data For - hottest dayhighlight Zone - Zone 1Zone settings - hVac - natural Ventilation

With no hVac system, the inside temperature of Zone 1 is hotter than the outside temperature at certain hours of the day. it is also above thermal comfort for most of the day.

search data For - hottest dayhighlight Zone - Zone 1Zone settings - hVac - mixed system

once the temperature goes above the set range, the ac kicks in and cools the interior.

hourly TemperaTure profile

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search data For - hottest dayhighlight Zone - Zone 1Zone settings - hVac - natural Ventilation

The graph shows that the largest amount of heat gain is due to direct solar. adding shading devices will help reduce this.

search data For - hottest dayhighlight Zone - Zone 1Zone settings - hVac - mixed system

When the hVac system is activated, the largest amount of hourly gains is due to the system. as before, adding shading devices could help reduce the amount the system needs to be used.

hourly heaT Gains/losses

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search data For - hottest dayhighlight Zone - Zone 1Zone settings - hVac - mixed systemWindow material - single glazed

The text data shows that the total heat gain due to the hVac is 22399.45 Btu.

search data For - hottest dayhighlight Zone - Zone 1Zone settings - hVac - mixed systemWindow material - double glazed low e

By switching to double glazed, low-e windows, the total heat gain due to the hVac is 18440.38 Btu. This is a reduction of over 17%.

hourly heaT Gains/losses

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highlight Zone - Zone 1Zone settings - hVac - natural Ventilation

This chart will show you the number of hours and percentage of time that the zone is in the bounds of the comfort temperature range with just natural ventilation. shown here, the temperature is only comfortable 1/3 of the time. The other 2/3 it would need to be heated or cooled.

Be sure your hours of operation are set, otherwise the results will be skewed.

highlight Zone - Zone 1Zone settings - hVac - natural Ventilationclimate: san Francisco

if the building were located in san Francisco instead of new york, there would be about the same number of hours in the comfort zone.

TemperaTure DisTribuTion

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highlight Zone - Zone 2south Facade - Brick

This graph shows the amount of heat gain strictly from solar for each hour, averaged monthly.

highlight Zone - Zone 2south Facade - single glazed

allowing the south facade to be glazed creates a significant increase in solar gain.

DirecT solar Gains

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highlight Zone - Zone 1Zone settings - hVac - natural Ventilation

another way to view the amount of comfort hours for a zone is through this calculation. make sure your zones are set to none or natural ventilation.

highlight Zone - Zone 1Zone settings - hVac - mixed system

if your zone is set to an hVac system, you can view the amount of heating or cooling needed per month for that zone. The top chart shows when the thermostat is set to 78 max. The bottom is at 82 max, thus reducing the cooling load.

monThly loaDs/DiscomforT

notes:

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passive Gains breakDown

This analysis will show you the areas of biggest concern for gains/losses in your building.

here you can see that heat loss through the external fabric is the largest contributor.

Thermal Analysis in Ecotect

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